1. Field of the Invention
The invention relates generally to a microwave polarization control network and more particularly to such a network capable of rotating the plane of polarization of the wave in the output dual mode waveguide.
2. Description of the Prior Art
Polarization control networks are knwon in the microwave prior art employing a dual mode transducer followed by a microwave section mountd on bearings for mechanical rotation to produce a rotating linear (if .DELTA..PHI.=180.degree.) or circular (if .DELTA..PHI.=90.degree.) polarization in the output. Such a scheme requires bearings and a motor to rotate and is complex and expensive and of slower speed than electrical switching. It is, however, capable of providing a multitude of polarizations.
Prior Art U.S. Pat. No. 4,266,203 Saudreau et al, controls the polarization after the energy has been radiated by an antenna, in other words, a space polarization screen. Configurations such as this provides some degree of control and have been around for some time.
U.S. Pat. No. 4,293,858 Hockham, discloses a variable polarization linear array which could be used as a line source feed for a cylindrical reflector or in a two-dimensional array forming a narrow beam in both planes.
The present invention provides a plurality of polarizations unlike Saudreau et al, and provides a polarization agility for either horn-type antennas, which radiate directly, or for smaller feed horns for doubly curved reflectors producing narrow beams, unlike Hockham, which could be used as a line source feed for a cylindrical reflector or in a two-dimensional array forming a narrow beam in both planes. The horn-type is best suited for ECM applications such as jamming. The doubly curved reflector finds most use in radar systems where polarization agility or switchability is desired for weather penetration (circular polarization) or ECCM. The type of orthogonal signals radiated by the present invention (right-hand circular and left-hand circular, vertical and horizontal linear, plus 45.degree. and minus 45.degree. linear) is selected by the switches within the four-port network.
The manner in which the present invention functions and its advantages over the prior art will be better understood as the description proceeds.